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排序方式: 共有262条查询结果,搜索用时 15 毫秒
81.
Örjan Berglund Kerstin Berglund Leif Klemedtsson 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(6):508-513
Abstract Methods used to estimate the CO2 emission from soil commonly measure the total CO2 flux. To be able to quantify the net CO2 emission from cultivated peat soils there is a need to distinguish between soil organic matter-derived CO2 respiration and plant-derived respiration. In this investigation we used the root exclusion method to separate the plant-derived respiration from total CO2 emission. The plant-derived contribution was estimated to be between 27 and 63% of total CO2 emission depending on soil type and season. We also found a relationship between soil temperature, biomass growth and CO2 efflux, which can be used to estimate plant-derived respiration. Due to the priming effect the root exclusion method is less reliable late in the season. 相似文献
82.
Poor compost quality and odor emission are often significant problems in the composting industry. Composting process control can potentially help reduce both of these problems. In spite of the recent development of a number of process control strategies, very few direct comparisons have been made between these, particularly in terms of compost quality and odor emission. To help address this need, a series of experiments were conducted to evaluate the effects of several in-vessel process control strategies on organic matter conversion, nitrogen transformation and pH, and odor emission. The strategies focussed on aeration control. Fixed aeration, temperature feedback, oxygen feedback, and combined temperature/oxygen feedback algorithms were tested. A modified algorithm called linear temperature feedback was also developed and tested. Results showed that the compost temperature profiles were quite similar for the various feedback control algorithms, whereas fixed rate aeration led to significantly higher temperature, as expected. Compost properties such as C:N ratio and organic matter loss were also similar between process control methods. However, oxygen content was maintained more consistently using oxygen feedback or linear temperature feedback algorithms. Linear temperature feedback is preferable to oxygen feedback in that it does not require oxygen sensors to operate. Mass emission rates of odorous gas (methyl mercaptan and dimethyl sulfide) were typically found to increase with higher aeration rates, such as those used to limit temperature, though the gas concentration was lower. For maximum retention of nitrogen, adequate supply of readily biodegradable carbon in the feedstock is vital. 相似文献
83.
Shift‐share analysis is a decomposition technique widely used in regional studies to quantify an industry‐mix effect and a competitive effect on the growth of regional employment (or any other relevant variable) relative to the national average. This technique has always been subject to criticism for its lack of theoretical basis. This paper presents a critical assessment of the methods suggested by Dunn and Esteban‐Marquillas and proposes a new shift‐share method, which separates out the two effects unambiguously. By way of illustration, we provide an application to manufacturing employment in the Belgian provinces between 1995 and 2007. 相似文献
84.
Distribution,structure and function of Nordic eelgrass (Zostera marina) ecosystems: implications for coastal management and conservation 下载免费PDF全文
Christoffer Boström Susanne Baden Anna‐Christina Bockelmann Karsten Dromph Stein Fredriksen Camilla Gustafsson Dorte Krause‐Jensen Tiia Möller Søren Laurentius Nielsen Birgit Olesen Jeanine Olsen Leif Pihl Eli Rinde 《水产资源保护:海洋与淡水生态系统》2014,24(3):410-434
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85.
Rachael K. Lau Anneke Moresco Sarah J. Woods Christopher M. Reilly Michelle G. Hawkins Christopher J. Murphy Steven R. Hollingsworth Dennis Hacker Kate S. Freeman 《Veterinary ophthalmology》2017,20(6):560-567
A juvenile to young adult, male, great horned owl (Bubo virginianus,GHOW) was presented to the wildlife rehabilitation hospital at Lindsay Wildlife Museum (WRHLWM) due to trauma to the right patagium from barbed wire entanglement. On presentation, both corneas were irregular, dry, and no movement of the third eyelid was noted. A severe corneal enlargement/globoid appearance was the predominant ophthalmic feature. The fundus was normal in both eyes (OU). Over the course of several days, both corneas developed edema combined with further dessication at the ocular surface associated with diffuse dorsal fluorescein stain uptake. Repeated ophthalmic examinations found normal intraocular pressures and an inability to move the third eyelid over the enlarged corneas. The bird was deemed nonreleasable due to severe wing damage and poor prognosis associated with eye abnormalities and was humanely euthanized. Postmortem CT, enucleation, and histopathology were performed to evaluate the ocular anatomical abnormality and confirm the suspected diagnosis of keratoglobus. This GHOW represents the first reported case of presumptive keratoglobus in a raptor. 相似文献
86.
Sidsel Jensen Henrik Oestdal Leif H. Skibsted Erik Larsen Anette K. Thybo 《Journal of Cereal Science》2011
Wheat bread and whole wheat bread were stored for up to 3 weeks and specific chemical reactions were related to perceptual flavour changes as analysed by sensory profiling. Volatile and non-volatile compounds were quantified using GC–MS and HPLC. Results were examined by multivariate data analysis. 相似文献
87.
Peri Jasmin Lau‐Gillard Peter Barrie Hill Christopher James Chesney Chis Budleigh Aki Immonen 《Veterinary dermatology》2010,21(2):136-145
In humans, transepidermal water loss (TEWL) is measured by noninvasive techniques using either open‐ or closed‐chamber instruments. The aim of this study was to investigate the use of a hand‐held, closed chamber device (Vapometer®) to measure TEWL in canine skin. Repeated measurements obtained from multiple body sites in one short and one long‐coated dog had mean coefficients of variation ranging from 20% to 33%. In the short‐coated dog, TEWL ranged from a mean of 5.8 g/m2/h on the ventral abdomen to 24.4 g/m2/h between the shoulders. In the long‐coated dog, mean TEWL values ranged from 26.3 g/m2/h on the right chest wall to 51.3 g/m2/h in the right axilla. TEWL readings differed significantly at different body sites and showed significant day‐to‐day variation. In a comparison of a further 20 dogs, TEWL readings obtained from the lateral thorax differed significantly between dogs. Furthermore, in seven of the twenty dogs, readings differed significantly when one side was compared with the other. The Vapometer® was able to measure TEWL in canine skin and yielded values similar to those previously reported in the literature using other devices. However, for use in clinical studies, the significant site to site, day‐to‐day and dog to dog variations would make changes induced by disease, drugs, dietary supplements or topical agents very difficult to reliably detect. 相似文献
88.
Oxidation of 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) by lactoperoxidase was found to be inhibited by tyrosine-containing random amino acid copolymers but not by tyrosine. Both electrostatic effects and polymer size were found to be important by comparison of negatively and positively charged copolymers of varying lengths, with poly(Glu, Tyr)4:1 ([E 4Y 1] approximately 40) as the strongest competitive inhibitor (EC 50 approximately 20 nM). This polymer did not form dityrosine in the presence of lactoperoxidase (LPO) and peroxide. Furthermore, incubation with tert-butyl hydroperoxide, as opposed to hydrogen peroxide, resulted in a peculiar long lag phase of the reaction between the redox intermediate compound II and [E 4Y 1] approximately 40, indicating a very tight association between enzyme and inhibitor. We propose that interactions between multiple positively charged areas on the surface of LPO and the polymer are required for optimal inhibition. 相似文献
89.
Liang J Tian YX Fu LM Wang TH Li HJ Wang P Han RM Zhang JP Skibsted LH 《Journal of agricultural and food chemistry》2008,56(21):10376-10383
Isoflavone daidzein (D, pK a1 = 7.47 +/- 0.02 and pK a2 = 9.65 +/- 0.07) was, through a study of the parent compound and its three methyl anisol derivatives 7-methyldaidzein (7-Me-D, pK a = 9.89 +/- 0.05), 4'-methyldaidzein (4'-Me-D, pK a = 7.43 +/- 0.03), and 7,4'-dimethyldaidzein (7,4'-diMe-D), found to retard lipid oxidation in liposomal membranes through two mechanisms: (i) radical scavenging for which the 4'-OH was more effective than the 7-OH group in agreement with the oxidation potentials: 0.69 V for 4'-OH and 0.92 V for 7-OH versus Ag/AgCl in acidic solution and 0.44 V for 4'-O(-) and 0.49 V for 7-O(-) in alkaline solution and (ii) change in membrane fluidity through incorporation of the isoflavones, in effect hampering radical mobility. The radical scavenging efficiency measured by the rate of the reaction with the ABTS(*)(+) in aqueous solution followed the order D > 7-Me-D > 4'-Me-D > 7,4'-diMe-D, as also found for antioxidant efficiency in liposomes when oxidation was initiated with the water-soluble AAPH radical and monitored as the formation of conjugate dienes. For oxidation initiated by the lipid-soluble AMVN radical, the antioxidant efficiency was ranked as 4'-Me-D > D > 7,4'-diMe-D > 7-Me-D, and change in fluorescence anisotropy of fluorescent probes bound to the membrane surface or inside the lipid bilayer confirmed the effects of isoflavones on the membrane fluidity, especially for 7,4'-diMe-D. 相似文献
90.
Background, Aims, and Scope As a consequence of human living and activity, water infiltration to the urban subsurface occurs from a variety of different
sources, like precipitation, irrigation, leaking pipes and sewers, septic tanks and rainwater infiltration ponds. This infiltration
is strongly related with quality issues of the infiltrated water and further impact on groundwater quality. In order to set
up an integrated urban water balance it becomes essential to estimate the infiltration processes, i.e. water flow and solute
transport, from these different infiltration sources and to take into account the large spatial variability of sediment properties,
the geometric settings of these sources and the groundwater table. For that purpose, the development of simple, physically-based
quantification approaches is required in order to establish an efficiently working prediction and risk analysis tool within
the framework of an integrated urban water management system. The scope of the presented work was to demonstrate the applicability
of the developed approaches at urban scale.
Methods Since a detailed, three-dimensional, numerical quantification of the infiltration processes within the entire urban area is
not possible, the individual sources were considered as independent within the EU AISUWRS project. Different models were developed
for balancing infiltration from areal and point sources with respect to the related flow pattern. The analytical model UL_FLOW,
based on one-dimensional, steady state analytical solutions, allows the estimation of conservative tracer residence times
in layered sediments under varying infiltration rates. The numerical model WSTM, based on a three-dimensional random walk
approach, calculates water and solute transport from pipe leaks. Additionally, the sources were classified in accordance to
the spatial distribution of the parameters determining the infiltration processes.
Results UL_FLOW was applied to data sets from the city of Rastatt within a case study of the AISUWRS project. Each neighbourhood of
water balance computation by the Urban Volume and Quality Model (UVQ) was defined as an areal infiltration source with unique
parameter values for sediment depth, profile and properties, as well as infiltration rate time series. Groundwater recharge
and residence time series were computed for each neighbourhood. Relevant statistical parameters obtained by time series analyses
from those time series could be mapped by GIS. Point infiltration, particularly from sewers, was classified due to the sediment
parameters and the distance to the groundwater table at each source location in order to reduce computational efforts. WSTM
computations provided time series of groundwater recharge and tracer breakthrough for some specific cases.
Discussion The analytical model UL_FLOW provides fast and efficient computation of groundwater recharge and residence times accounting
for storage effects within the unsaturated zone of urban areas. The reliability of this model has been shown by cross validation
with HYDRUS1D. Because of the high computational effort, WSTM could provide only short-term simulations for some specific
parameter sets for which residence time estimates could be derived.
Conclusions UL_FLOW provides an analytical modelling tool for balancing one-dimensional areal infiltration and estimating residence times
under varying conditions including spatial parameter variability. These balances could be used for assessing the impact of
those infiltration sources on groundwater quality. The tracer breakthrough from point infiltration sources computed by WSTM
could also be used for such kinds of assessment. The larger spatial parameter variability associated with these sources could
be handled by classification in GIS environments.
Recommendations and Perspectives Similar to the areal sources, a simple balance approach for point sources based on analytical solutions needs to be developed
for estimating residence times in order to avoid large computational efforts. Such a model would complete the balancing of
all kinds of infiltration sources in urban areas efficiently. Since the approaches are based on the balance of the physical
processes, they have a large predictive capability and could be included into an integrated urban water balance and management
system. The mapping of the statistical values of the residence times provides a tool to compare parts of the urban areas and
to visualize differences between urban water management scenarios. 相似文献